ADP is stored in dense bodies inside bloodplatelets and is released upon platelet
activation. ADP interacts with a family of ADP receptors found on
platelets (P2Y1, P2Y12 and
P2X1), leading to further platelet activation.[1] ADP in
the blood is converted to adenosine by the action of ecto-ADPases,
inhibiting further platelet activation via adenosine
receptors. The anti-platelet drug Plavix (clopidogrel) inhibits
the P2Y12 receptor.

ADP is the end-product that results when ATP loses one of its
phosphate groups located at the end of the molecule.[2
] The conversion of these two molecules plays a
critical role in supplying energy for many processes of life.[2
] The deletion of one of ATP’s phosphorus bonds
generates approximately 7.3 kilocalories per Mole of ATP.[3]
ADP can be converted, or powered back to ATP through the process of
releasing the chemical energy available in food; in humans this is
constantly performed via aerobic respiration in the
mitochondria.[2
] Plants use photosynthetic pathways to convert
and store the energy from sunlight, via conversion of ADP to
ATP.[3]
Animals use the energy released in the breakdown of glucose and
other molecules to convert ADP to ATP, which can then be used to
fuel necessary growth and cell maintenance.[2
]